Excerpts from Paul Dagleish's messages
Message dated 3 November 2015
1st excerpt from:
The first automatic temperature controller was designed and programmed by me. I spent some time visiting possible manufacturers around Europe and finally chose ASL (Automatic Systems Laboratories Ltd) in England after having put out a call for tender to various companies (cannot remember which). ASL was at that time at the forefront of temperature resistance measurement with their automatic AC Bridge invented by their PDG Peter C. F. Wolfendale.
I baptised this controller the PTC (Precision Temperature Controller). It was the first temperature controller totally piloted by microprocessor - the Motorola MC6809 which had an 8-bit bus and 16-bit internal registers. The control programme was a simple loop continually monitoring the four temperature measurement channels, displaying their values, calculating and PID control algorithm and setting an appropriate heater value. The loop communicated with the main instrument via a standard RS232 serial port.
A huge step forward in removing experimental errors was the introduction of thermometer calibrations for each individual cryostat. This was achieved using simple plug-in modules containing the calibrations on EPROM. Each module, one for the sample holder and one for the cryostat regulation block, contained two sets of calibration for the Platinum and Carbon thermometers. The module for the regulation block also contained optimum PID values for the given cryostat. This meant that for the first time at the ILL sample temperatures could be automatically set without human supervision.
The updated version, ILLSEC (ILL Sample Environment Controller), was also designed by me with help from “le gone lyonnais”, Guy Drevetton. It was constructed by www.duhameldti.fr Domène. It had much better electronics and a proper real-time operating system, OS9, running on the MC68030 32-bit microprocessor. Each measurement channel had its own 16-bit microprocessor so that temperature measurement could be much more rapid and accurate. Each ILLSEC contained the complete calibration and control parameters for the whole ILL. Each sample environment apparatus (cryostat, cryofurnace etc) was fitted with a system that transmitted its unique identity to the ILLSEC thus reducing the chance of calibration errors sometimes introduced by not using the correct calibration modules in the old PTC.